Study On Aerodynamic Characteristics Of Wheel

With the country's emphasis on energy conservation and environmental protection,automobile aerodynamics have been increasingly valued in China in recent years.For vehicle drag reduction,because the resistance of the wheels in the vehicle exceeds 30%,simulation and experimental follow-up studies are urgently needed.Achieving accurate measurement of wheel aerodynamics and accurate capture of flow structure is the key to the study of wheel aerodynamic characteristics.Based on the related research,this paper independently designed the test bench for experimental research,including wheel aerodynamic measurement and PIV flow field measurement.The simulation uses STAR-CCM + software overlapping mesh to realize the real wheel-to-ground rotation of the wheel,and studies the flow mechanism of the wheel free flow under fixed conditions and rotating conditions.In this paper,the accuracy of the simulation is verified by the flow field experiment of the long cylinder,and then the flow characteristics of the short cylinder are studied.The ground-around flow of the long cylinder belongs to two-dimensional flow,and the short cylinder belongs to three-dimensional flow.Through comparison,it is found that although the separation around the top of the short cylinder is delayed and the return vortex is more stable under fixed conditions,the horseshoe vortex and wheel shoulder are formed due to the side airflow Vortex,a large amount of energy loss results in greater resistance than the long cylinder;after the two are rotated,the early separation of the airflow around the top brings different effects,the resistance of the long cylinder increases and the resistance of the short cylinder decreases.Continue to study the flow structure of three wheel scale models with different chamfers,and compare the flow mechanisms of the three in fixed and rotating conditions.Because of the existence of chamfers,the wheels may have different eddy current structures.The rotation mainly affects the shoulder vortex and horseshoe vortex to determine different aerodynamic characteristics.At the same time,it is found that the rotation has a stable airflow to reduce the turbulence and reduce drag.On the basis of studying the flow structure of the scale model,continue to study the flow mechanism of the more complex college student racing wheel.The main flow structure of the racing wheel has a high similarity to the flow structure of the contraction model,but because of The existence of wheel cavity flow will bring great influence.The flow mechanism of the wheel cavity is different from that of the fixed and rotating conditions.The vortex of the wheel cavity also causes the asymmetry of the entire vortex pair of the racing wheel.The rotation measured by the experiment makes the drag coefficient of the racing wheels decrease by 15% compared with the fixed working conditions of the wheels,and it decreases by 95 counts.The effect is obvious.Further study of the aerodynamic characteristics of wheels in different rim states found that the gradual closure of the rim area will have different effects on the flow structure.Under fixed operating conditions,the resistance will increase with the increase of the rim closed area,but under the rotating operating conditions,the resistance will Gradually decrease.This article successfully designed an experimental bench capable of measuring wheel rotation force,which can measure the resistance and aerodynamic torque in fixed and rotating conditions,but the lift force in rotating conditions cannot be accurately measured.The numerical values of the simulation and the measured values of the bench are different from each other in the absolute values of the specific working conditions,but the relative values of the simulation and the experimental conditions have very high accuracy.It strongly supports the research on aerodynamic characteristics of racing wheels with different rim states.